1. Field of the Invention
The present invention relates to an image processing apparatus able to encode and decode moving images in parallel, or encode the same moving image by a plurality of systems having different image qualities in parallel, and an image processing method thereof.
2. Description of the Related Art
In recent years, image recording and reproducing apparatuses which record moving images as digital data on recording media using the MPEG (Moving Picture Experts Group) or other compressive encoding schemes and reproduce the same have come under attention. Particularly, video recorders for home use able to write on digital versatile disks (DVD), hard disks, or both as recording media have become popular.
Some of the image recording and reproducing apparatuses using disk type recording media have the function of recording certain moving image content and reproducing other content recorded in the past in parallel or the function of recording content and reproducing the recorded part of the content during that operation, that is, “time-shift” reproduction. These functions are realized by recording and reproducing moving images simultaneously. At this time, for example MPEG encoding processing and decoding processing are simultaneously carried out. Conventional image recording and reproducing apparatuses have been provided with separate encoding circuits and decoding circuits for this purpose.
Further, there is also a demand for the functions of recording image data on recording media and simultaneously recording the same content at a different resolution, compression rate, or format to portable semiconductor memories or other recording media in parallel or transmitting it over a network. These functions are realized by carrying out the encoding processings for producing the image data simultaneously. Conventional image recording and reproducing apparatuses have carried out the processing using separate encoding circuits.
Japanese Unexamined Patent Publication (Kokai) No. 9-322121 discloses the following image decoding apparatus able to perform encoding processing of one system of data and decoding processing of another system of data in parallel. The decoding apparatus is provided with an inverse transform circuit used for both coding and decoding data. A signal input as a high efficiency encoded image signal and run through a variable length decoding circuit and an inverse quantizer circuit and an input image signal of another system are selected by a multiplexing circuit and input to the inverse transform circuit, the former signal is decoded at and output from the inverse transform circuit, and the latter image signal is encoded at the inverse transform circuit, then output via a quantizer circuit and variable length coding circuit. Here, the inverse transform circuit is operated at two times or more the real time speed to enable the inverse transform circuit to be used and switched between the decoding function and the coding function and enable the decoding processing and the coding processing to be performed in parallel.
Summarizing the disadvantages to be overcome by the invention, when providing separate encoding circuits and decoding circuits for performing the encoding processing and the decoding processing of images simultaneously as described above, the circuit size is increased. Further, when providing a plurality of separate decoding circuits for producing image data having different resolutions in parallel, the circuit size similarly ends up being increased. To prevent an increase in circuit size, the method of having the circuits for encoding and decoding share a frame memory for temporarily storing image data may be considered. However, in this case, it is necessary to increase the data transfer rate of the frame memory, whereby the component becomes higher in cost.